What term describes a cold air mass replacing a warm air mass?

• A. Cold Front
• B. Warm Front
• C. Occluded Front
• D. Stationary Front

Answer: (A)

When a colder air mass slides in and replaces a warmer air mass, the boundary between them is a cold front. The cold air, being denser, wedges beneath the warm air and forces it upward. That lifting often brings rapid changes in weather, including a sharp drop in temperature behind the front, a shift in wind direction, and the potential for clouds, heavy rain, or thunderstorms as the warm air condenses quickly.

The other terms describe different interactions: a warm front is when warm air moves in to replace cold air, typically bringing light, more prolonged precipitation and a gradual temperature rise. An occluded front happens later in a storm when a cold front catches up with a warm front and the warm air is forced aloft. A stationary front is when neither air mass advances, leading to ongoing weather along the boundary.